Centrifugal fan assemblies typically include a centrifugal fan positioned in a scroll-shaped housing or volute. The housing typically includes an inlet through which air or gas is drawn by the centrifugal fan, and an outlet through which pressurized air or gas is discharged. Centrifugal fans typically include a plurality of blades that pressurize and/or accelerate an incoming axial airflow for discharge into a scroll portion of the housing. The blades are typically attached to a hub for rotation therewith. The hub typically defines an airflow surface on the base of the centrifugal fan to redirect the incoming axial airflow toward a radial direction for discharge into the scroll portion of the housing.
Centrifugal fan assemblies also typically include a tongue positioned in the scroll-shaped housing to separate the scroll-portion of the housing from a discharge portion of the housing, which includes the outlet. The tongue is typically positioned in close proximity to the centrifugal fan to guide the airflow exiting the centrifugal fan into the scroll portion of the housing and to separate off a portion of the airflow that entered the scroll portion.